Method and apparatus for initiating in situ combustion



C. L. BAUER Filed Feb. 28, 1968 METHOD AND APPARATUS FOR INITIATING IN SITU COMBUSTION July i4, 1970 w m fw ,/a /L a er A v N .r www@ m ff gt f uw l 7 XMB O0 M .O00 k u .w oMMWMJ, owmww M 2 4 WM W, W 2 Z v Al rj Q c /w/ww W Hw\// \M e 7T; f l il 7 l 0,00 Wws fs QC Qq u L. 000%0 Mw z f V m n h X M k u United States Patent O 3,520,364 METHOD AND APPARATUS FOR INITIATING IN SITU COMBUSTION Charles L. Bauer, New York, N.Y., assignor to Texaco Inc., New York, N.Y., a corporation of Delaware Filed Feb. 28, 1968, Ser. No. 708,915 Int. Cl. E21b 43/24 U.S. Cl. 166-260 9 Claims ABSTRACT OF THE DISCLOSURE A method of initiating in situ combustion in an underground hydrocarbon-bearing formation wherein a selfcontained ignition package with a lower chamber containing a fuel pack and means for ignition therefor and with an upper chamber containing an additional supply of fuel is placed adjacent the stratum to be ignited subsequent to the injection of a liquid having a relatively low self-ignition temperature and flash point thereinto.

BACKGROUND OF THE INVENTION This invention relates generally to a method of and apparatus for treatment of a subterranean formation. More particularly, this invention relates to the generation of heat in a well bore penetrating into a hydrocarbon-bearing stratum.

In modern day production of hydrocarbons from subterranean formations, it is common practice to apply secondary recovery techniques to recover additional quantities of hydrocarbons therefrom, One of the more common secondary recovery techniques currently employed is that of in situ combustion. In this method of producing hydrocarbons, combustion is initiated in the hydrocarbon-bearing stratum by means of an igniter positioned in a well bore adjacent thereto. Once the stratum has been successfully ignited, a combustion supporting fluid, e.g., an oxygen-containing gas such as compressed air, is injected into the well bore to support the combustion front and move it through the stratum towards a production well. Alternatively, reverse in situ combustion, viz, a method wherein the hydrocarbons are produced through the same well as was used for injection and ignition of the stratum, has proven quite effective also.

In order to accomplish successful in situ combustion, it is necessary that ignition of the formation be sufficient to subsequently sustain uniform movement of the combustion front throughout the stratum. Successful ignition is generally dependent upon generating a sufficient temperature to support and propagate a combustion front. Among the techniques for initiating in situ combusion included in the prior art are various types of ignitors, including downhole heaters, electrical heating devices, chemical compounds and other combustibles placed into the well bore. The results derived from the utilization of many of these techniques has been less than satisfactory, primarily due to the fact that sufficiently high temperatures were not generated within the time required to successfully ignite the formation and establish a uniform combustion front. The invention herein disclosed provides a means for generating sufficiently elevated temperatures to initiate in situ combustion, these temperatures being generated in a relatively short period of time, and also provides means for successfully ignitng the formation across any desired length of stratum.

SUMMARY OF THE INVENTION The invention herein disclosed provides an improved method of and apparatus for generating sufficiently high temperatures adjacent a hydrocarbon-bearing stratum to successfully initiate in situ combustion therein. A uni- 3,520,364 Patented July 14, 1970 form combustion front in the stratum is established by injecting a liquid having a relatively low self-ignition temperature and flash point thereinto prior to the ignition of a fuel pack. The fuel pack is contained in the lower chamber of the ignition package and is positioned adjacent the stratum to be ignited. High temperatures are generated by combustion of the fuel pack and maintained for a time sufficient to insure uniform ignition of the stratum by replenishing the fuel as it is consumed.

The principal advantage Amade `possible by the use of this invention over the prior art is that an effective and economic means is provided for successful ignition of an in situ combustion process. Injection of a liquid having a relatively low self-ignition temperature and flash point into the hydrocarbon-bearing stratum insures that the rate of temperature build-up in the formation will be within a short period of time and produce a uniform combustion front throughout the crude contained in the formation. Further, the apparatus herein disclosed permits accurate placement of the ignition package adjacent the stratum desired to be ignited. Once combustion of the fuel pack is accomplished by means of ignitors placed therein, sufficient additional fuel is provided in the upper chamber of the apparatus in order to sustain combustion thereof and achieve sufficient temperatures to uniformly ignite the formation.

Accordingly, it is a primary object of this invention to provide an effective method of and apparatus for initiating in situ combustion and establishing a uniform combustion front throughout the formation.

A further object of this invention is to provide a method of and apparatus for generatingl sufficiently high ternperatures adjacent the desired stratum to initiate in situ combustion therein.

These and other objects, advantages and features of the invention will become more apparent from the following description taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION `OF THE DRAWING FIG. l depicts an elevation view, partly in cross section, of a well bore having positioned therein the ignition package; and

FIG. 2 is an elevation view, partly in cross section, of the ignition package positioned in the well bore and containing an air line passing therethrough.

DESCRIPTION OF THE PREFERRED EMBODIMENT Successful in situ combustion as a secondary recovery technique is primarily dependent upon effective ignition of the formation. Frequent attempts in using in situ combustion wherein recoveries from the formation were insubstantial have been attributed to the fact that the formation was not amenable to in situ combustion. Undoubtedly, failure of some of these attempts was due to reality to the fact that no discrete ordered zones of fluid movement were established in the formation, although some limited ignition may have occurred. Random combustion, wherein various localized combustion centers are spread throughout the formation, precludes the establishment of a uniform combustion front in the formation. Whether one is attempting forward or reverse in situ combustion, the effectiveness thereof is dependent on a uniform combustion front wherein there are no localized air fluxes.

A uniform combustion front which will progress through the formation and -provide an effective sweep thereof is accomplished by the establishment of an ignition train as disclosed herein. With reference to the drawings, the ignition train is established by injection into the stratum adjacent the well bore 10, one or more materials having a self-ignition temperature lower than that of the crude contained in the formation. The injected material also serves to displace from the stratum any undesirable materials having an adverse dilution effect. Packers (not shown) may be provided in the well casing 11 at the top and bottom of the hydrocarbon-bearing stratum to provide for direct injection of materials thereinto. The materials used to establish the ignition train depend upon the type of crude in the formation to be ignited. Specifically, when igniting a formation containing a low gravity crude, a 17.8 API crude and a 41.0 API kerosene have been successful in the establishment of a uniform combustion front. The injected materials having an ignition temperature lower than that of the crude contained in the formation, will ignite more readily and subsequently provide effective and uniform ignition of the crude. The injected materials may be ignited readily by either spontaneously ignitable chemicals or a down-hole ignitor. The injected materials introduce little or no adverse dilution of the formation since they contribute to the amount of heat generated and also displace any adverse diluents, such as water, which may have been initially present therein.

Successful ignition of the injected fiuid may best be accomplished by the ignition package indicated at 20, which consists basically of an upper chamber 21 interconnected to a lower chamber 22. The lower chamber 22 is fabricated from a sheet metal material indicated at 23, and is provided with perforations along the entire length thereof. The ignition package 20 is inserted into the well bore with the lower chamber 22 being approximately the same size as the well bore diameter and placed adjacent the stratum to be ignited. The placement of the ignition package in the well bore 10 may be accomplished by means of the spacer 24 attached to the base of the lower chamber 22 and seated on the bottom of the well bore. The length of the spacer 24 is dependent upon the particular depth of the well and location of the hydrocarbon-bearing stratum with respect thereto.

Preferably the fuel pack 25, housed in the lower chamber 22, is charcoal presoaked with kerosene, although other materials may be substituted. Alternatively, the fuel pack 25 may comprise charcoal in combination with an oxygen bearing compoundselected from the group of alkali metal salts such as chlorates, permanganates, nitrates and combinations thereof, thereby eliminating the necessity of introducing a combustion supporting gas during the initial combustion phase. The upper chamber 21, attached by means of the collar 26 to the lower chamber 22, contains an additional supply of fuel 27, similar to that contained in the lower chamber 22, to replenish that consumed by combustion in the lower chamber and insure generation of sufficiently high temperatures within the time required for establishment of a uniform combustion front. With the length of the lower chamber 22 approximately twice that of the upper chamber 21, sufficient volume is provided in the latter chamber to maintain an adequate supply of reverse fuel therein. As indicated in FIG. 1, the upper chamber 21 has attached to the top thereof a tubing string 28. The tubing string 28 is connected to an air supply (not shown) located at the surface of the well bore 10 and provides a meansv for introducing a combustion supporting gas into the ignition package 20. Alternatively, the ignition package 20 may be lowered into the well bore by means of a cable and air injected into the formation through the opening 12 in the well bore and thereby eliminate the requirement for a tubing string. lf it is so desired, the upper chamber 21 may be designed to contain a supply of compressed air therein and thereby provide a selfcontained package which is capable of supporting combustion of the fuel pack 25 in the lower chamber 22. Spaced in the fuel pack 25 are a plurality of ignitors indicated at 29a, 29b and 29C. These ignitors are responsive to an electrical signal generated at the surface of the well bore and provide a means for initiating combustion of the fuel pack 25. The number and spacing between the ignitors is dependent upon the length of stratum to be heated.

Referring to FIG. 2, the ignition package 20 is depicted with a tubing string 30 passing therethrough. The tubing string 30 is connected to an air supply (not shown) located at the surface of the well bore and provides a means for introducing combustion supporting gas into the fuel pack 25. The lower portion of the tubing string 30 is perforated as indicated at 30a for the portion extending into the lower chamber 22 and thereby provides a means for direct introduction of air into the combustible portion of the fuel pack.

Usage of the ignition package 20 'has indicated that temperatures in excess of 2000 F. in a relatively short period of time can be attained adjacent the stratum to be ignited. Temperatures of this value insure uniform and complete ignition of the fuels previously injected into the formation. A uniform combustion front of the crude contained in the formation is achieved by means of the ignition train previously discussed and provides for optimum recovery from the hydrocarbon-bearing formation.

Once the formation has been successfully ignited, continued injection of a combustion supporting gas may be utilized to drive the combustion front toward an adjacent production well and recovery of hydrocarbons may be made therethrough. Alternatively, it may be found advantageous to discontinue injection of the combustion supporting gas and use water to drive the combustion front toward the adjacent production well.

Other modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. An apparatus for generating heat in a well bore which comprises:

(a) a hollow tubular member having an upper and lower chamber means interconnected with.,each other,

(b) said lower chamber means being formed of a perforate material containing therein a fuel pack with means of ignition thereof contained therewithin,

(c) said upper chamber means having attached thereto means for lowering said tubular member into said well bore and housing an additional supply of fuel for replenishing that consumed by combustion in lower chamber means,

(d) means for positioning said tubular member in said well bore adjacent to the hydrocarbon-bearing stratum to be heated.

2. An apparatus as defined in claim 1 wherein said fuel. pack comprises a carbonaceous material presoaked with a hydrocarbon fiuid.

3. An apparatus as defined in claim 2 wherein said carbonaceous material is presoaked with kerosene.

4. An apparatus as defined in claim 1, wherein said fuel pack comprises charcoal in combination with an oxygen bearing compound selected from the group of alkali metal salts consisting of chlorates, permanganates, nitrates and combinations thereof.

5. An apparatus as defined in claim 1,'wherein said means for ignition comprises a plurality of ignitors spaced predeterminately throughout said fuel pack and responsive to an electrical signal generated at the surface of said well bore. l

6. An apparatus as defined in claim 1, in combination with a means for introducing air into said tubular member for support of combustion in said lower chamber.

7. An apparatus as defined in claim 1, wherein said tubular member includes' a spacer attached to the bottom thereof in order` to position said fuel pack adjacent to the hydrocarbon-bearing stratum to be heated.

8. An apparatus for generating heat in a well bore which comprises:

(a) a hollow tubular member having an upper and a lower chamber means interconnected with each other,

(b) said lower chamber means being formed of a perforate material and containing therein a charcoal fuel pack presoaked with a hydrocarbon fluid,

(c) said fuel pack having spaced therein a plurality of ignitors responsive to an electrical signal generated from the surface of said well bore for initiating combustion thereof,

(d) said upper chamber means containing therein an additional charcoal fuel pack for replenishing that consumed by combustion in said lower chamber means,

(e) a tubing string extending through said tubular member and containing along the lower portion thereof a plurality of perforations adjacent to said fuel pack in said lower chamber means, said tubing string being in operative communication with a source of combustion supporting gas and providing means for introducing said last mentioned gas into said fuel pack to support combustion thereof, and

(f) means for positioning said tubular member in said well bore adjacent the hydrocarbon-bearing stratum to be heated.

9. Method of recovering hydrocarbons from a subterranean hydrocarbon-bearing formation traversed by an injection well and a production well spaced therefrom which comprises:

(a) introducing via said injection Well bore into said hydrocarbon-bearing formation a kerosene having a low flash point,

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(b) introducing into said injection well bore a means for generating heat comprising a fuel pack with means of ignition thereof contained therewithin,

(c)introducing via said injection well bore a combustion supporting gas into that portion of said hydrocarbon-bearing formation containing said kerosene having said low flash point,

(d) effecting ignition of said fuel pack,

(e) continuing injection of said combustion supporting gas via said injection well bore into said formation,

(f) recovering hydrocarbons from said production STEPHEN I. NOVOSAD, Primary Examiner U.S. Cl. X.R. 166--58, 262 

